A wide variety of coatings have been used to coat the surfaces of packaging articles (e.g., food and beverage cans). For example, metal cans are sometimes coated using “coil coating” or “sheet coating” operations, i.e., a planar coil or sheet of a suitable substrate (e.g., steel or aluminum metal) is coated with a suitable composition and hardened (e.g., cured). The coated substrate then is formed into the can end or body. Alternatively, liquid coating compositions may be applied (e.g., by spraying, dipping, rolling, etc.) to the formed article and then hardened (e.g., cured).
Packaging coatings should preferably be capable of high-speed application to the substrate and provide the necessary properties when hardened to perform in this demanding end use. For example, the coating should be safe for food contact, have excellent adhesion to the substrate, and resist degradation over long periods of time, even when exposed to harsh environments.
Many current packaging coatings contain mobile or bound bisphenol A (“BPA”) or aromatic glycidyl ether compounds or PVC compounds. Although the balance of scientific evidence available to date indicates that the small trace amounts of these compounds that might be released from existing coatings does not pose any health risks to humans, these compounds are nevertheless perceived by some people as being potentially harmful to human health. Consequently, there is a strong desire to eliminate these compounds from food contact coatings.
From the foregoing, it will be appreciated that what is needed in the art is a packaging container (e.g., a food or beverage can) that is coated with a composition that does not contain extractible quantities of such compounds.